RHSA-2003:224 - Security Advisory

Topic

Updated OpenSSH packages are now available. These updates close an
information leak caused by sshd's interaction with the PAM system.

Description

OpenSSH is a suite of network connectivity tools that can be used to
establish encrypted connections between systems on a network and can
provide interactive login sessions and port forwarding, among other functions.

When configured to allow password-based or challenge-response
authentication, sshd (the OpenSSH server) uses PAM (Pluggable
Authentication Modules) to verify the user's password. Under certain
conditions, OpenSSH versions prior to 3.6.1p1 reject an invalid
authentication attempt without first attempting authentication using PAM.

If PAM is configured with its default failure delay, the amount of time
sshd takes to reject an invalid authentication request varies widely enough
that the timing variations could be used to deduce whether or not an
account with a specified name existed on the server. This information
could then be used to narrow the focus of an attack against some other
system component.

These updates contain backported fixes that cause sshd to always attempt
PAM authentication when performing password and challenge-response
authentication for clients.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade. Only those
RPMs which are currently installed will be updated. Those RPMs which are
not installed but included in the list will not be updated. Note that you
can also use wildcards (*.rpm) if your current directory *only* contains the
desired RPMs.

Please note that this update is also available via Red Hat Network. Many
people find this an easier way to apply updates. To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

Affected Products

• Red Hat Enterprise Linux Server 2 ia64
• Red Hat Enterprise Linux Server 2 i386
• Red Hat Enterprise Linux Workstation 2 ia64
• Red Hat Enterprise Linux Workstation 2 i386

Fixes

• BZ - 98594 - CAN-2003-0190 OpenSSH valid username information leak

CVEs

• CVE-2003-0190

References

(none)